Dramatic improvements in computer processing power and broadband streaming technology have lead to the development of interactive systems for navigating imagery (e.g., map imagery). Some interactive map navigation systems provide a user interface (UI) with navigation controls for dynamically navigating cities, neighborhoods and other terrain in three dimensions. The navigation controls enable users to tilt, pan, rotate, zoom and activate terrain and buildings for different perspectives at a point of interest. An example of an interactive 3D map system for navigating Earth imagery is Google Earth™ developed by Google Inc. (Mountain View, Calif.).
The production imagery used by interactive map navigation systems is typically derived by processing large pieces of geo-located imagery or “assets,” which can be taken from a single pass of a satellite or stitched together from multiple aerial photos. Once the imagery is processed it can be moved to datacenters where it can be distributed to client devices.
As a user manipulates the navigation controls of an interactive map system hosted on a client device, the map system will periodically request new imagery, terrain and/or vector data (e.g., gas stations, restaurants, points of interest, etc.) from the datacenters. Prior to making these requests, the map system needs to know if such data is available at the point of interest for the requested level of detail. For example, if a user zooms into a location on the Earth to see more detail, the map system needs to know if data is available, so that such data can be requested from the datacenter. Requesting data from a datacenter when no data is available, or when the data is already available to the mapping system, consumes bandwidth and can be wasteful.